Radar systems have long been known and widely employed to locate physical bodies, such as vessels, airplanes, bodies of land, and the like. There have also been developed a substantial number of improvements and extensions of basic radar systems including automatic tracking systems for target, collision calculators and collision warning systems. Prior art cited in U.S. Pat. No. 3,660,846, and U.S. patent application Ser. No. 680,685, filed Apr. 27, 1976 for "AUTOMATIC COLLISION WARNING TARGET DISPLAY SYSTEM," is in part, relevant to various of these developments. Automatic warning systems are set out in the above-noted patent and patent application, and the present invention is an extension thereof particularly with regard to warning of drifting of a vessel at anchor although the present invention has other uses, as noted below.
Many, if not most, ocean-going vessels are equipped with some type of radar, although some are quite rudimentary, however, such systems normally have only a limited utility, i.e. location of physical bodies or targets and displaying the information. The above-noted patent and patent application extend the utility of radar systems, but do not extend the utility into vessel at anchor conditions except insofar as possible collision is concerned. It is conventional on a vessel at anchor to have the bridge watch check bearings of fixed objects to guard against drift of the vessel at anchor as by dragging the anchor. The present invention is capable of performing this operation, among others, to thus relieve personnel of this task and also to preclude human error.